Solubility Lab

In this lab, the main objective is to identify the identity of an unknown compound via the methods of extraction, recrystallization, and melting point determination (University of Windsor, 2015). An important factor in this experiment is solubility. Solubility is the affinity for one solvent over the other. Liquids, or aqueous solutions, that may dissolve the same compound are commonly found to be miscible. By using liquid – liquid extraction a compound can transform into an ionic form, soluble in polar solvents (water), through acid-base reactions. Examples of organic molecules having ionizable functional groups which can be separated using acid-base reactions are as follows:

The interaction of stronger acids and bases produce weaker conjugated acids and bases. The reaction may fully proceed in a forward direction depending on the relative acidity and basicity of both the reactants and the products (Karty, 2014). To measure the strength of an acid, the dissociated constant, Ka, is used. The Ka, value is measured based on how easily the acid donates a hydrogen ion and is therefore measured in terms of pKa: pKa = - log Ka …show more content…
Carboxylic acids are the most acidic (pKa around 5) and phenols are weaker acids in comparison to carboxylic acids (pKa around 10). With the addition of NaHCO3 and NaOH, strong bases, the carboxylic acid and phenol are much stronger acids resulting in the reaction proceeding in the forward